There are several types of field-driven particles in the field of non-emissive displays. One class uses the so-called electrophoretic particle that is based on the principle of movement of charged colloidal particles in an electric field. In an electrophoretic display, the charged particles containing different reflective optical densities can be moved by an electric field to or away from the viewing side of the display, which produces a contrast in the optical density. Another class of field-driven particles are particles carrying an electric dipole. Each pole of the particle is associated with a different optical densities (bi-chromatic). The electric dipole can be aligned by a pair of electrodes in two directions, which orient each of the two polar surfaces to the viewing direction. The different optical densities on the two halves of the particles thus produces a contrast in the optical densities.
To produce a high quality image, it is essential to form a plurality of image pixels by varying the electric field on a pixel wise basis. The electric fields can be produced by a plurality pairs of electrodes embodied in the display as disclosed in U.S. Pat. No. 3,612,758. One difficulty is in displaying color images. The field-driven particles of different colors need to be provided in discrete color pixels. This approach requires the colored particles to be placed in precise registration corresponding to the electrodes. This approach is therefore complex and expensive.
An additional problem in the displays comprising field-driven particles is forming images that are stable. Typically the images on these displays must be periodically refreshed to keep the image from degrading.
Small size is a highly desirable feature in a product or subsystem. High levels of integration tend to reduce system size and cost. It is desirable to improve the integration of display devices. System complexity is reduced by integration; the integration of a display will allow the display to be operated with fewer auxiliary devices.